JPH0780970B2 - Method for manufacturing water-absorbent composite material - Google Patents

Description

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method for producing a water-absorbing composite material comprising a water-absorbing polymer and a molded fibrous substrate. More specifically, the present invention provides a highly water-absorbing polymer formed by applying an aqueous acrylic acid-based monomer solution to a molded fibrous substrate, polymerizing the monomer to form a composite precursor, and further crosslinking the composite precursor. The present invention relates to a method for producing a water-absorbent composite material fixed to a fibrous base material.

The water-absorbent composite material obtained by the production method of the present invention is excellent in water absorbency, and since the superabsorbent polymer is fixed to the fibrous substrate with good stability, it is advantageously used for production of various water-absorbent materials. be able to.

2. Description of the Related Art Conventionally, paper, pulp, non-woven fabric, sponge-like urethane resin, etc. have been used as various water-retaining agents such as sanitary napkins, various kinds of sanitary materials such as paper naps, and various agricultural materials. However, since the water absorption amount of these materials is only about 10 to 50 times their own weight, a large amount of material is required to absorb or retain a large amount of water, and not only becomes extremely bulky, In addition, there is a drawback in that moisture is easily released when the water-absorbed material is pressurized.

In order to improve the above-mentioned drawbacks of this type of water absorbing material, various high water absorbing polymer materials have been proposed in recent years. For example, starch graft polymer (Japanese Patent Publication No. 53-46199, etc.), modified cellulose (Japanese Patent Publication No. 50-80376, etc.),
Crosslinked water-soluble polymer (Japanese Patent Publication No. 43-23462, etc.), self-crosslinking alkali metal acrylate polymer (Japanese Patent Publication No. 54
-30710, etc.) was proposed.

However, although these water-absorbent polymer materials have a considerably high level of water-absorbing performance, most of them are obtained in the form of powder, and therefore, for example, sanitary napkins,
In order to use it as a sanitary material such as a paper sheet, it is necessary to uniformly disperse it on a substrate such as tissue, non-woven fabric or cotton. However, it is difficult to stably fix the polymer powder dispersed by such a method on the base material, and it is likely that the polymer powder partially aggregates after the dispersion, and the swollen gel after water absorption is stable. It is not fixed on the base material and easily moves from the base material. For this reason, when this is used, for example, in a paper squeeze, the water absorbent body after urination becomes a "stiff" state, which makes it extremely uncomfortable to wear. In addition, the method of obtaining the absorbent body by dispersing the powdery polymer as described above in the substrate is costly because of the complexity involved in handling the powder and the process problems in efficiently performing uniform dispersion. It is extremely expensive.

As one method for solving these problems, a composite obtained by applying an acrylic acid-based monomer aqueous solution to a fibrous substrate molded in a predetermined pattern is produced, and then irradiated with electromagnetic radiation or particulate ionizing radiation. , A method of producing a water-absorbing complex by converting an acrylic acid-based monomer into a super-water-absorbing polymer has been reported (Japanese Patent Publication No. 57-500546). According to this method, although there is a considerable improvement in terms of uniform dispersion in handling the above powder and stable immobilization on the substrate, in converting to a super absorbent polymer, Due to the use of electromagnetic radiation or particulate ionizing radiation, the superabsorbent polymer inherent in this particular monomer is too susceptible to cross-linking reactions, resulting in
The obtained composite has a remarkably small performance as an absorber, especially a water absorption capacity, and it seems that there is a drawback that it is usually less than half that in the case where the powdery superabsorbent polymer is used.

Further, recently, in JP-A-60-149609, a water-soluble radical polymerization initiator or a water-soluble radical polymerization initiator and a water-soluble reduction agent are prepared by impregnating a water-absorbing organic material with an aqueous solution of an acrylate-based monomer in advance. There has been proposed a method for producing a water-absorbing composite material in which the agent is atomized, added and polymerized. However, in this method, since the water-soluble polymerization initiator is added after the water-absorbing organic material is impregnated with the acrylic acid-based monomer, “polymerization unevenness” occurs even if the polymerization initiator is atomized, It is extremely difficult to completely polymerize the monomer, and as a result, the amount of residual monomer is large, and there are many safety problems, and it seems that there are drawbacks in terms of performance, especially in water absorption.

Possible Solution Against this background, the present inventors have already filed Japanese Patent Application No. 60-193403.
No. 25, the aqueous solution of an acrylic acid-based monomer having a monomer concentration of 25% by weight or more and a water-soluble radical polymerization initiator or a water-soluble radical polymerization initiator and a water-soluble reducing agent are uniformly mixed in advance, and a high water absorption property in the fibrous substrate Polymer particle size
A method of applying the mixture to a fibrous substrate formed by atomizing the mixture so as to have a particle size of 30 to 500 μm, and then polymerizing the mixture is disclosed in Japanese Patent Application No.
-202908, a highly water-absorbent polymer in a fibrous substrate after previously uniformly mixing an aqueous solution of an acrylic acid monomer containing a small amount of a crosslinking agent and a water-soluble radical polymerization initiator or a water-soluble radical polymerization initiator and a water-soluble reducing agent. Particle size 30-500
A method of applying the mixture to a fibrous substrate formed into a mist so as to have a size of μm and then polymerizing the mixture is disclosed in Japanese Patent Application No. 60-238421.
Japanese Patent Application No. 2003-242242, a method of mixing an aqueous solution of an acrylic acid monomer containing a small amount of a cross-linking agent and an oxidizable radical polymerization initiator, and then applying to a fibrous substrate, and then applying an amine or a reducing agent to perform polymerization. After mixing an aqueous solution of an acrylic acid monomer containing a small amount of a cross-linking agent and an amine or a reducing agent in JP 60-238420 A, a fibrous substrate is applied, and then an oxidizing radical polymerization initiator is applied to perform polymerization.
And so on.

These methods are considerably improved in terms of uniform dispersion in handling the powder as described above and stable fixation on the base material, but the water absorption rate is still small, and especially sanitary napkins, paper naps, etc. It was a problem when used as a sanitary material.

[Outline of Invention]

OBJECT OF THE INVENTION The present invention includes the above-mentioned Japanese Patent Publication No. 57-500546 and JP-A-60-
Japanese Patent Application No.
-193403, Japanese Patent Application No. 60-202908, Japanese Patent Application No. 60-238421,
And a method of further improving the water-absorbing composite proposed in Japanese Patent Application No. 60-238420 to produce a water-absorbing composite having a large water-absorbing performance, particularly a particularly large water-absorbing speed under mild conditions. It is the one we are trying to provide.

The present inventors have conducted various studies for the purpose of solving the above-mentioned problems, and as a result, applied an acrylic acid-based monomer aqueous solution to a molded fibrous substrate, polymerize the acrylic acid-based monomer, and then, By cross-linking with a carboxyl group and / or a carboxylate group, a water-absorbing composite material having a large water-absorbing performance, particularly a particularly high water-absorbing rate, and a highly water-absorbing polymer fixed on a fibrous substrate with good stability can be obtained. The present invention has been achieved by finding that it can be easily and inexpensively obtained.

That is, the method for producing a water absorbent composite material according to the present invention is characterized by comprising the following steps of bonding.

(A) A step of applying to a molded fibrous substrate an aqueous solution of a polymerizable monomer containing acrylic acid as a main component in which 20% or more of carboxyl groups are neutralized with an alkali metal salt or an ammonium salt.

(B) A step of polymerizing the polymerizable monomer applied to the fibrous substrate to form a composite of the polymer derived from the polymerizable monomer and the fibrous substrate.

(C) The above complex has a carboxyl group and / or
A crosslinking agent compound having two or more functional groups capable of reacting with the carboxylate group is added in an amount of 0.01 to 10 parts by weight of water per 1 part by weight of the polymer derived from the polymerizable monomer in the composite. A step of adding and reacting in the existing state.

EFFECTS OF THE INVENTION In the method for producing a water-absorbing composite material of the present invention, most of acrylic acid-based monomers applied to a molded fibrous substrate are polymerized into a super-water-absorbing polymer, so that the water-absorbing performance is increased. Further, the water-absorbent polymer is crosslinked to have a particularly high water-absorption rate, and the highly water-absorbent polymer is stably fixed to the fibrous substrate,
It has remarkable features in terms of the above. Therefore, a water-absorbent composite material, which is far superior to the above-mentioned prior inventions, can be obtained easily and at low cost.

The crosslinking treatment in the step (C) in the present invention uses the carboxyl group and / or the carboxylate group of the acrylic acid-based polymer in the composite obtained in the step (B) as crosslinking points. Since it is understood that the water absorption of the complex is at least partly due to the presence of the carboxyl group and / or the carboxylate group, the water absorption rate can be improved by modifying the hydrophilic group in step (C). It can be said that the improvement was unexpected.

[Specific Description of the Invention]

Step (A) and (B) Monomer The monomer used in the present invention contains acrylic acid as a main component, but 20% or more, preferably 50% or more thereof is neutralized with an alkali metal salt or an ammonium salt. There is something. If the degree of partial neutralization is less than 20%, the water absorption performance of the produced polymer is significantly deteriorated, which is not preferable.

Further, in the present invention, in addition to the acrylic acid and the acrylic acid salt, a monomer copolymerizable with them, for example, 2-acrylamido-2-methylpropanesulfonic acid, 2-acryloylethanesulfonic acid, 2-acryloylpropanesulfonic acid, Methacrylic acid and its alkali metal salts or ammonium salts, (meth) acrylamide, N, N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl ( Water absorption performance by adding one or more selected from the group consisting of (meth) acrylate, polyethylene glycol mono (meth) acrylate, N, N′-methylenebis (meth) acrylamide and polyethylene glycol di (meth) acrylate. Gayo There are cases where high is obtained. Here, "(meth) acrylic" means acrylic and methacrylic. Other monomers copolymerizable with acrylic acid and acrylates, for example water-soluble monomers such as itaconic acid, maleic acid, fumaric acid, vinylsulphonic acid and their alkali metal or ammonium salts, are also included in the invention. As long as the “aqueous solution of polymerizable monomer” is formed, a low water-soluble monomer such as alkyl acrylates such as methyl acrylate and ethyl acrylate can be used in combination.

Since the "polymerizable monomer" in the present invention is mainly composed of acrylic acid (of which 20% or more is in the form of a salt), the amount of the above-mentioned copolymerizable monomer added is generally In
It is less than 50 mol%, preferably 20% or less.

It should be noted that alkali metal hydroxides, bicarbonates, ammonium hydroxides, etc. can be used for neutralizing the above-mentioned acid monomers including acrylic acid, but alkali metal oxides are preferable. There are sodium hydroxide, potassium hydroxide and lithium hydroxide as specific examples. Sodium hydroxide or potassium hydroxide is preferred from the viewpoints of industrial availability, price, and safety.

In the present invention, the acrylic acid as described above (of which 20%
The above is a salt) and a polymerizable monomer mainly containing the above is applied to the fibrous base molded article in the form of an aqueous solution. The concentration of the aqueous solution in this case can be any value that is purposeful. Specifically, for example, 30% by weight or more is suitable.

This aqueous solution may contain various substances as long as it is not against the object of the present invention. An example of such a substance is an aqueous solution radical polymerization initiator (detailed later). Also,
"The aqueous solution may be a solution of a small amount of a water-soluble organic solvent, if desired.

Molded fibrous substrate The molded fibrous substrate to which the above aqueous polymer solution is to be applied is
Specifically, a loosely formed fiber, for example, a pad, a carded or air-laid web, a tissue paper, a woven cloth such as cotton gauze,
It is a knitted fabric or a non-woven fabric. Where "molded"
The fibrous base material means a material which may require cutting, joining, shaping, or the like for incorporating the fibrous base material into a product, but does not require further web forming work.

It is generally preferred to use absorbent fibers such as wood pulp, rayon, cotton or other cellulosic fibers and / or polyester fibers as the major component in the fibrous substrate. However, other types of fibers such as polyethylene, polypropylene, polystyrene, polyamide, polyvinyl alcohol, polyvinyl chloride,
Fibers such as polyvinylidene chloride-based, polyacrylonitrile-based, polyurea-based, polyurethane-based, polyfluoroethylene-based, and polyvinylidene cyanide-based fibers may be contained in a molded fibrous substrate.

Application of Aqueous Monomer Solution and Polymerization of Monomer (Primary Polymerization) In the present invention, the above-mentioned aqueous monomer solution is applied to the molded fiber substrate, and the monomer is polymerized on the fiber substrate (primary polymerization).

The aqueous monomer solution can be applied to the molded fibrous substrate by any purposeful means or modes as long as the monomer can be uniformly dispersed and held on the fibrous substrate and polymerized. One of the typical means for this is to impregnate the fibrous substrate with the aqueous monomer solution or to spray the aqueous monomer solution onto the fibrous substrate.

A preferred embodiment of applying the monomer aqueous solution to the fibrous substrate is to apply the monomer aqueous solution so as to form a continuous linear pattern along the fibers of the molded fibrous substrate, or to apply it in small periodic dots on the fibers. is there. In the former embodiment, a method of impregnating or spraying a large amount of an aqueous monomer solution onto a molded fibrous substrate to adhere or impregnate the fibers, and then removing the aqueous monomer solution between the fibers by suction or applying by a roll coater is used. Apply to molded fiber substrate. In the latter embodiment, the aqueous monomer solution is applied by spraying on the molded fibrous substrate, in which case the particle size is 30 to
It is preferable to set the spraying conditions so as to be about 500 μm, preferably about 30 to 200 μm.

Also, the step of polymerizing the monomer uniformly dispersed on the fibrous substrate in this manner may be a purposeful one. A typical example of such a method is by the action of a water-soluble radical polymerization initiator, specifically, the radical polymerization initiator is added to an aqueous monomer solution and decomposed on the fibrous substrate. Alternatively, the radical polymerization initiator is uniformly applied to the fibrous substrate after application of the monomer solution as a solution separate from the monomer by spraying or the like to decompose on the fibrous substrate, or the radical polymerization initiator is different from the monomer. The solution is applied to the fibrous substrate as another solution, and the aqueous monomer solution is uniformly applied thereto by spraying or coating. Another means of initiating polymerization is irradiation with high energy radiation.

The water-soluble radical polymerization initiator used in the present invention is well known in the field of polymer chemistry. Specific examples include inorganic or organic peroxides such as persulfates (ammonium salts, alkali metal salts (particularly potassium salts) and the like), hydrogen peroxide, ditertiary butyl peroxide, acetyl peroxide, and the like. In addition to these peroxides, azo compounds and other radical polymerization initiators such as 2,2'-azobis (2-amidinopropane) dihydrochloride can be used as long as a predetermined water solubility is obtained. .

Polymerization is initiated by the decomposition of these radical polymerization initiators, but heating which is a conventional means for decomposition (the temperature at the time of contact with the monomer is often already the decomposition temperature, especially heating is (In this specification, the case where the polymerization is started only by adding the polymerization initiator to the monomer is not included in the scope of the decomposition by heating in this specification), and the decomposition of the polymerization initiator is promoted by chemical substances. Doing is also a well-known means. When the polymerization initiator is a peroxide, the decomposition accelerating substance is a reducing compound (a water-soluble compound in the present invention) such as an acid sulfite, ascorbic acid, amine or the like for a persulfate. A polymerization initiator composed of a combination of an oxide and a reducing compound is well known in the field of polymer chemistry as a "redox initiator". Therefore, in the present invention, the term "polymerization initiator" includes a combination with such a decomposition promoting substance, particularly a redox initiator.

High energy radiation includes electromagnetic radiation and fine particle ionizing radiation.

Such polymerization initiation means, in particular, the polymerization of acrylic acid (of which 20% or more is in the form of a salt) -based monomer with a water-soluble radical polymerization initiator produces N, N'-methylenebis ( It should be a non-crosslinked water-soluble polymer unless a diethylenic monomer such as (meth) acrylamide is used, but in practice it is between acrylic acid (salt) or its polymers or / and between fibrous substrates. It is recognized that a crosslinking reaction occurs. Therefore, polyacrylic acid (salt) produced in this process
Is a superabsorbent polymer rather than a water-soluble polymer.

The polymerization with the water-soluble radical polymerization initiator should be substantially aqueous solution polymerization. Therefore, step (B) should be carried out avoiding excessively dry conditions.

The amount of the monomer applied to the fibrous substrate in the step (A) is 1 to 10,000 parts by weight per 100 parts by weight of the fibrous substrate,
It is preferably 10 to 1000 parts by weight. At least 50%, preferably at least 80% of the monomers applied in this way should be polymerized in step (B). 80 in process (B)
It is usual to obtain a polymerization rate of about 95%.

Based on the above, some of the specific examples of the steps (A) and (B) are shown below.

(1) An acrylic acid-based monomer aqueous solution having a monomer concentration of 25% or more and a water-soluble radical polymerization initiator are uniformly mixed in advance, and the superabsorbent polymer particle size in the fibrous substrate is 30 to 50.
A method in which the mixed solution is atomized to a particle size of 0 μm and applied to a molded fibrous substrate, and when the polymerization initiator is not a redox system, heating is performed to perform polymerization (see Japanese Patent Application No. 60-193403).
(2) An aqueous solution of an acrylic acid-based monomer containing a small amount of a cross-linking agent and a water-soluble radical polymerization initiator are uniformly mixed in advance, and then mixed so that the superabsorbent polymer particle size in the fibrous substrate is 30 to 500 μm. A method in which the liquid is atomized and applied to a molded fibrous substrate, and when the polymerization initiator is not a redox type, the polymerization is carried out by heating (see Japanese Patent Application No. 60-202908), (3) Acrylic containing a small amount of a crosslinking agent An aqueous solution of an acid-based monomer and an oxidizing radical polymerization initiator are mixed on a fibrous substrate,
Thereafter, a method of applying a amine or a reducing agent to form a redox system to initiate polymerization (see Japanese Patent Application No. 60-238421), (4) an aqueous solution of an acrylic acid-based monomer containing a small amount of a crosslinking agent, and an amine Or a reducing agent is mixed and then applied to a fibrous substrate, and then an oxidizing radical polymerization initiator is applied to form a redox system to initiate polymerization (see Japanese Patent Application No. 60-238420), (5) ) A method of impregnating a fibrous substrate with an acrylic acid-based monomer aqueous solution in advance and then adding a water-soluble radical polymerization initiator in the form of a mist, and heating the polymerization initiator by heating when the polymerization initiator is not a redox system (special (Kaisho 60-149609 publication) and so on.

Step (C) Crosslinking Treatment The crosslinking treatment is carried out with a crosslinking agent compound having at least two functional groups which react with the carboxyl group and / or carboxylate group derived from the polymer in the composite obtained as described above. Consists of reacting.

The above-mentioned functional groups of the crosslinking agent compound used in the present invention include an ethoxy group, an aldehyde group, an alkyl hydroxyl group, a primary to secondary amine group, and others.

A compound having at least two such functional groups is, therefore, ethylene glycol diglycidyl ether,
Examples thereof include polyglycidyl ethers such as polyethylene glycol diglycidyl ether, haloepoxy compounds such as epichlorohydrin, polyaldehydes such as glutaraldehyde and gluoxal, polyols such as ethylene glycol and glycerin, and polyamines such as ethylenediamine. Among these, polyglycidyl ethers are preferable.

The cross-linking reaction can be proceeded by uniformly adding the cross-linking agent compound to the complex from the step (B) and reacting it. In that case, it is the water content of this complex that should be noted. That is, if this complex contains excessive water, and if it is excessively dried, efficient cross-linking does not occur, and the combined effect of the water absorption rate aimed at by the present invention is extremely small. Will end up. The water content of the composite is from 0.01 to 1 part by weight of the polymer derived from the polymerizable monomer in the composite.
10 parts by weight, especially 0.1 to 1 part by weight.

The amount of the crosslinking agent compound added is the amount of the polymer derived from the polymerizable monomer.
It is about 0.01 to 10%, preferably 0.1 to 5% (by weight).

The crosslinking reaction conditions vary depending on the kind of the crosslinking agent compound used, but generally 50 to 200 ° C., preferably 100 to 15
The temperature is about 0 ° C. and the time is about several seconds to 5 hours, preferably several seconds to 1 hour.

Since the amount of the crosslinking agent compound used is small as described above, in order to uniformly add such a small amount of the crosslinking agent compound to the complex from the step (B), it is necessary to apply, spray or impregnate in the form of a solution. Good.

The reaction method or device can be any purposeful. Specifically, for example, a method of heating the inside in a batch manner by a box-type reactor set to a predetermined temperature, continuous heating in which a target complex is continuously brought into contact with a roller set to a predetermined surface temperature by steam or the like. There are other ways.

The atmosphere during heating may be either under vacuum or in the presence of an inorganic gas such as nitrogen, argon or helium, or in air. The preferred atmosphere is air.

Experimental Example Example 1 Sodium hydroxide (purity 9
(6% by weight) 13.1 g was taken, and 30 g of acrylic acid was gradually added thereto under ice cooling to neutralize. The degree of neutralization was about 75%, and the monomer concentration in the aqueous solution was about 45% by weight.

0.05% of potassium persulfate as a radical polymerization initiator
g was taken, dissolved in the above monomer aqueous solution, and degassed with N ₂ .

Separately, 0.583 g of a polyester non-woven fabric was taken, and the above-mentioned aqueous monomer solution was applied to the whole surface of the non-woven fabric by a roll coater to form a linear pattern along the fibers. The amount of the impregnated monomer was 6.8 times the weight of the nonwoven fabric. This was placed in a constant temperature reaction vessel that had been degassed with N ₂ in advance to 90 ° C. Polymerization occurred immediately, and a superabsorbent polymer consisting of a self-crosslinked product of partially neutralized sodium polyacrylate was fixed to the polyester nonwoven fabric along the fibers in a linear pattern with good stability.

Next, the water content of this complex was adjusted to about 25% by weight (based on the weight of the superabsorbent polymer; hereinafter the same), 0.017 g of ethylene glycol diglycidyl ether was sprayed as a solution, and then set to 120 ° C. It was placed in a constant temperature layer for 15 minutes to obtain a water absorbent composite material.

The properties of the obtained water-absorbent composite material were as follows (the same applies to the following production examples).

Example 2 13.1 g of sodium hydroxide (purity: 95% by weight) was placed in a 100 cc conical flask and dissolved in 39.0 g of pure water under ice cooling. To this, 30 g of acrylic acid was poured under ice cooling for neutralization. The degree of neutralization of acrylic acid was about 75%, and the monomer concentration in the aqueous solution was about 45% by weight. N, N ′ as a crosslinkable monomer
0.005 g of methylenebisacrylamide and 0.1 g of 2,2'-azobis (2-amidinopropane) dihydrochloride as a radical polymerization initiator were taken, dissolved in the aqueous monomer solution and deaerated.

Separately, 0.655 g of a polyester non-woven fabric was taken, and the above raw materials were applied to the entire surface of the non-woven fabric by a roll coater to form a linear pattern along the fiber. The amount of the impregnated monomer was 7.5 times the weight of the nonwoven fabric. This was placed in a constant temperature reaction tank that had been degassed with N ₂ in advance and kept at 90 ° C. Polymerization occurred immediately, and a superabsorbent polymer consisting of N, N'-methylenebisacrylamide cross-linked product of partially neutralized sodium polyacrylate was stably fixed to the polyester non-woven fabric along the fiber in a linear pattern. A complex was obtained.

Next, the water content of this complex was adjusted to about 28% by weight, and 0.025 g of ethylene glycol glycidyl ether was added to the mixture to give 120%.
It was placed in a constant temperature layer set at 0 ° C for 15 minutes to obtain a water absorbent composite material.

Example 3 30 g of acrylic acid was placed in a 100 cc conical flask, and 9.3 g of pure water was added thereto and mixed. To this, potassium hydroxide (85% by weight) 20.6 was gradually added under ice cooling to neutralize, and the temperature was maintained at 70 ° C. The degree of neutralization is about 75%, and the monomer concentration in the aqueous solution is about 74.
It became weight%.

Separately, 0.2 g of potassium persulfate was added to water as a radical polymerization initiator.
It dissolved in 3.0 g.

Separately, 0.5869 g of rayon nonwoven fabric was sampled and kept at about 70 ° C. in a constant temperature bath. Immediately after the radical polymerization initiator aqueous solution was mixed with the monomer aqueous solution, the non-woven fabric was sprayed from a spray nozzle. Polymerization immediately took place in the nonwoven fabric, and a composite was obtained in which the superabsorbent polymer consisting of a self-crosslinked product of partially neutralized potassium polyacrylate was fixed to the polyester nonwoven fabric with good stability. The amount of the applied monomer was 12 times the weight of the nonwoven fabric, and the particle size of the superabsorbent polymer was 100 to 300 μm.

Next, the water content of this composite was adjusted to 25% by weight, 0.038 g of ethylene glycol diglycidyl ether was added thereto, and the mixture was placed in a thermostat set at 120 ° C for 15 minutes to obtain a water-absorbing composite material. It was

Example 4 26.0 g of 25% ammonia water was placed in a 100 cc conical flask, and 30 g of acrylic acid was gradually added dropwise under ice cooling to neutralize and the temperature was raised to 70 ° C. The degree of neutralization was 95%, and the monomer concentration in the aqueous solution was about 55% by weight.

Separately, 0.2 g of potassium persulfate was added to water as a radical polymerization initiator.
Dissolved in 3 g.

Separately, 0.4695 g of polyester non-woven fabric was sampled and kept at about 70 ° C. in a constant temperature bath. Immediately after the radical polymerization initiator aqueous solution was mixed with the monomer aqueous solution, the non-woven fabric was sprayed from a spray nozzle. Polymerization immediately occurred in the nonwoven fabric, and a composite having a highly water-absorbent polymer composed of a self-crosslinked product of partially neutralized ammonium polyacrylate stably fixed to the polyester nonwoven fabric was obtained. The amount of the applied monomer was 8 times the weight of the nonwoven fabric, and the particle diameter of the superabsorbent monomer was 100 to 250 μm.

Next, the water content of the complex was adjusted to 15% by weight, and 0.021 g of ethylene glycol diglycidyl ether was added to this to obtain 12
It was placed in a constant temperature bath set at 0 ° C. for 15 minutes to obtain a water absorbent composite material.

Example 5 30 g of acrylic acid was placed in a 100 cc conical flask, and 16.9 g of pure water was added thereto and mixed. Under ice cooling, 20.6 g of potassium hydroxide (85% by weight) was gradually added to neutralize. The degree of neutralization is about 75%, and the monomer concentration in the aqueous solution is about
It was 65 weight.

Take 0.1 g of N, N'-methylenebisacrylamide as a cross-linking agent and add to the above monomer solution to dissolve it.
Warmed to. In addition to this, 31% as a radical polymerization initiator
0.4 g of hydrogen peroxide water was taken and dissolved.

Separately, 0.6521 g of a polyester non-woven fabric was taken, and the above raw materials were applied and impregnated on the entire surface of the non-woven fabric by a roll coater and kept at 40 ° C. in a constant temperature reaction tank. The amount of the impregnated monomer was 6.9 times the weight of the nonwoven fabric.

Next, a 5% L-ascorbic acid aqueous solution as a reducing agent was sprayed onto the entire surface of the non-woven fabric through a spray nozzle. Polymerization occurred immediately, and a superabsorbent polymer consisting of N, N'-methylenebisacrylamide crosslinked product of partially neutralized potassium polyacrylate was stably immobilized on the polyester nonwoven fabric to obtain a composite.

Next, the water content of this composite was set to about 30% by weight, 0.023 g of ethylene glycol diglycidyl ether was added thereto, and the mixture was treated for 15 minutes in a constant temperature reaction tank kept at 120 ° C to give a water-absorbing composite material. Obtained.

Example 6 30 g of acrylic acid was placed in a 100 cc flask, and 16.9 of pure water was added to it.
g was added and mixed. Add potassium hydroxide (8
(5 wt%) 20.6 g was gradually added to neutralize. Neutralization degree is about
It was 75%, and the monomer concentration in the aqueous solution was about 65% by weight.

Separately, 0.6925 g of polyester non-woven fabric was taken, and the above raw materials were applied to the entire surface of the non-woven fabric and impregnated with a roll coater. The amount of the impregnated monomer was 7.5 times the weight of the nonwoven fabric.

Next, the non-woven fabric impregnated with the partially neutralized potassium acrylate monomer aqueous solution was irradiated with an electron beam at a dose of 20 megarads from an electron beam apparatus equipped with a dynamitron accelerator. Polymerization occurred immediately, and a superabsorbent polymer consisting of a self-crosslinked body of partially neutralized potassium polyacrylate was fixed to the polyester nonwoven fabric along the fibers in a linear pattern with good stability.

Next, the water content of this composite was adjusted to 25% by weight, and 0.029 g of ethylene glycol diglycidyl ether was added thereto,
The mixture was treated for 15 minutes in a constant temperature reaction vessel kept at 120 ° C to obtain a water absorbent composite material.

Example 7 A water absorbent composite material was obtained by the same procedure and operation as in Example 1, except that 0.025 g of propylene glycol diglycidyl ether was used in place of the ethylene glycol diglycidyl ether in Example 1.

Example 8 A water absorbent composite material was obtained by the same procedure and operation as in Example 3, except that 0.045 g of neopentyl glycol diglycidyl ether was used in place of the ethylene glycol diglycidyl ether in Example 3. .

Example 9 Instead of ethylene glycol diglycidyl ether in Example 5, glycerol polyglycidyl ether 0.04
A water-absorbent composite material was obtained by the same procedure and treatment as in Example 5, except that 0 g was used.

Comparative Examples 1 to 6 The composites obtained in Examples 1 to 6, that is, the composites obtained without adding ethylene glycol diglycidyl ether were designated as Comparative Examples 1 to 6, respectively.

With respect to the water-absorbent composite materials obtained in the above Examples and the composites obtained in Comparative Examples, the following tests of physiological saline water absorption capacity and unpolymerized monomer concentration were conducted. The result is the first
It was as shown in the table.

A. About 0.5g of composite or water-absorbent composite material in a beaker with a physiological saline absorption capacity of 300ml.
And about 200 g of a 0.9% strength by weight saline solution were weighed and put therein, respectively, and allowed to stand for about 4 hours to sufficiently swell the polymer with the saline solution. Then, after draining with a 100-mesh sieve, the amount of super saline solution is weighed, and the physiological salt water absorption capacity is calculated according to the following formula.

B. Weigh about 800 g of 0.9 wt% saline in a beaker with a water absorption rate of 300 ml. Next, about 0.5 g of composite or absorbent composite
Weigh and place in this saline solution. After 5 minutes, water was drained through a 100-mesh sieve, the amount of the super saline solution was weighed, the physiological saline absorption capacity was determined based on the above formula, and this was taken as the water absorption rate.

The results are shown in the table below.

The water-absorbent composite material obtained by the production method of the present invention has a remarkably high water-absorption rate as compared with the preceding inventions and the like, as is clear from the above Examples and Comparative Examples. Furthermore, since its form is a sheet, it is easier to handle and cheaper than powdered water-absorbent resins that have been used conventionally,
It can be advantageously used for manufacturing various sanitary materials such as sanitary napkins and diapers.

Also, by utilizing its excellent water absorption performance and handleability,
The product according to the present invention can also be used for the production of various materials for horticultural or agricultural purposes such as soil improvers and water retention agents, which have recently been receiving attention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location C08F 2/00 MCT 265/02 MQM C08J 5/24 CEY 7310-4F D06M 13/11 15/263 D06M 13/18

Claims (11)

[Claims] 1. A method for producing a water-absorbing composite material, which comprises the following steps. (A) A step of applying to a molded fibrous substrate an aqueous solution of a polymerizable monomer containing acrylic acid as a main component in which 20% or more of carboxyl groups are neutralized with an alkali metal salt or an ammonium salt. (B) A step of polymerizing the polymerizable monomer applied to the fibrous substrate to form a composite of the polymer derived from the polymerizable monomer and the fibrous substrate. (C) The above complex has a carboxyl group and / or
A crosslinking agent compound having two or more functional groups capable of reacting with the carboxylate group is added in an amount of 0.01 to 10 parts by weight of water per 1 part by weight of the polymer derived from the polymerizable monomer in the composite. A step of adding and reacting in the existing state. 2. The method according to claim 1, wherein the polymerizable monomer comprises acrylic acid having 20% or more of carboxyl groups neutralized with an alkali metal salt or an ammonium salt. 3. The polymerizable monomer comprises up to 20 mol% of 2-acrylamido-2-methylpropanesulfonic acid, 2-acryloylethanesulfonic acid, 2-acryloylpropanesulfonic acid, methacrylic acid, and alkali metals thereof. Salt or ammonium salt, acrylamide, methacrylamide, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, polyethylene The method according to claim 1, which comprises at least one monomer selected from the group consisting of glycol monoacrylate and polyethylene glycol monomethacrylate. 4. The method according to claim 1, wherein the fibrous substrate molded in the step (A) has a cellulosic fiber and / or a polyester fiber as a main component. The method described in the section. 5. The fibrous substrate of step (A) is a loose pad of fibers, a carded web, an airlaid web, paper, a non-woven fabric, a woven fabric, or a knitted fabric.
The method according to any one of claims 1 to 4. 6. The step of applying the aqueous solution of the polymerizable monomer in step (A) to the molded fibrous substrate comprises spraying the aqueous solution onto the fibrous substrate or impregnating the aqueous solution with the fibrous substrate. A method according to any one of claims 1 to 5, consisting of: 7. The amount of the polymerizable monomer applied to the fibrous substrate in the step (A) is 1 to 1 per 100 parts by weight of the fibrous substrate.
The method according to any one of claims 1 to 6, which is 0000 parts by weight. 8. The method according to claim 1, wherein the polymerization in step (B) is carried out by the action of a water-soluble polymerization initiator. 9. The step of polymerizing the polymerizable monomer in the step (B) by the action of the water-soluble radical polymerization initiator is to dissolve the polymerization initiator in an aqueous solution of the polymerization monomer to decompose it. Alternatively, the method according to claim 8, which comprises spraying a polymerization initiator in a solution state on a fibrous substrate and then decomposing the fibrous substrate. 10. The crosslinker compound in step (C) has a glycidyl group as a group that reacts with a carboxyl group and / or a carboxylate group, and any one of claims 1 to 9. The method according to item 1. 11. The method according to claim 10, wherein the compound having a glycidyl group is polyglycidyl ether.